<html>
<head>
    <title>reCAPTCHA demo: Simple page</title>
    <script src="https://www.recaptcha.net/recaptcha/api.js" async defer></script>
    <script>
        function onSubmit(token) {
            document.getElementById("demo-form").submit();
        }
    </script>
</head>
<body>
<form id='demo-form' action="/watertap/check" method="POST">
    <!-- data-sitekey 需要填写公钥 -->
    <div class="g-recaptcha" data-sitekey="6Lc2MbEUAAAAAJFHTkvPJho_xcvYFbewq0Eoxren" data-callback='onSubmit'>Submit</div>
    <br/>
</form>
</body>
</html>